One of the problems with standardized vehicle seats and, more particularly, automotive vehicle seats is that they do not fit every driver especially the supportive portions of the backrest of the seat. This is particularly true in the lumbar area where the small of the back of the driver engages the backrest. Lack of proper lumbar support can be a major factor in bringing on driving fatigue in a person driving a motor vehicle.
In general, the use of a lumbar support regulating apparatus in the seat back of a motor vehicle seat is known so that the hardness of the cushion of the seat back which is in contact with the lumbar region of the person seated on the seat can be suitably regulated.
For example, U.S. patent of Sandor U.S. Pat. No. 3,378,299 discloses pivoted lever members in the back seat. One arm of a lever engages the seat spring to vary the firmness thereof and the arm of the lever is connected to a cable which may be wound up on rotatable shaft to vary the force with which the lever is pressed against the seat spring.
Many manually adjustable lumbar pressure mechanisms cannot be conveniently adjusted by the seat occupant when the driver is in the vehicle seat. Such an adjustment is particularly difficult when the driver must make a multi-turn adjustment before the desired contour can be obtained.
Some prior patents attempted to overcome the difficulties associated with such manual adjustment mechanism by providing a power-driven lumbar support mechanism. For example, the U.S. patent of Beyer U.S. Pat. No. 3,807,794 discloses a lumbar support mechanism including a reversible power mechanism coupled to a shaft which is operable to vary the pressure applied to a supporting pressure member. Likewise, the U.S. patent of Easley U.S. Pat. No. 3,890,000 discloses a lumbar support member which is controlled by a motor-driven adjusting screw rod which operates a crank arm on a rock shaft carrying a lumbar support member in the form of a contoured plate.
Other prior patents disclose adjustable lumbar supports wherein the adjustment of the supports is accomplished at the side of the backrest by the seated occupant. For example, the U.S. patent of Hayashi U.S. Pat. No. 4,019,777 discloses a lumbar support regulating apparatus wherein a torsion spring is wrapped about a vertically extending post secured to the frame of a seat back. One arm of the torsion lever is secured to a plate which is disposed and in engagement with the seat springs and the opposite end of the torsion spring is engaged with a traveling nut threaded on a rotatable control shaft so that upon rotation of the shaft the force applied to the torsion spring will be varied to adjust the support pressure applied to the seat springs. Likewise, the U.S. patent of Yoshimura U.S. Pat. No. 4,162,807 discloses a lumbar support regulating apparatus wherein the torsion spring is wrapped about a vertically extending post, the ends of the springs being operatively engaged with a lumbar plate and wherein an intermediate portion of the spring extends outwardly from the post in engagement with the rotatable cam having surfaces of different radii engageable with the intermediate portion of the spring to vary the force of the torsion spring.
Other lumbar support regulating apparatus generally of the type to which this invention relates are disclosed by the U.S. patents of Obermeier et al U.S. Pat. No. 3,948,558, Obermeier et al U.S. Pat. No. 3,973,797 and Arndt et al U.S. Pat. No. 4,182,533.
The present invention provides an improved lumbar support regulating apparatus which eliminates many of the drawbacks associated with the above-mentioned conventional regulating devices.